1. Technical Field
The present invention relates to a method for treating disease or condition susceptible to amelioration by AMPK activators and compounds of formula which are useful to activate AMP-activated protein kinase (AMPK) and the use of the compounds in the prevention or treatment of disease, including pre-diabetes, type 2 diabetes, syndrome X, metabolic syndrome and obesity.

2. Description of Related Art
Adenosine 5′-monophosphate-activated protein kinase (AMPK) is a cellular energy sensor and a responder to energy demand. AMPK is a heterotrimer composed of catalytic α subunit and regulatory β, γ subunits. All these subunits are highly conserved in eukaryotes. The activation of AMPK is through phosphorylation on the conserved 172th-threonine residue of α subunit by upstream kinasessuch as LKB1, Ca2+/Calmodulin dependent kinase, and TAK1. High AMP/ATP ratio caused by physiological or pathological stress activates AMPK. Upon activation, AMPK activates catabolic pathway and inhibits anabolism which in term restores cellular energy balance by decreasing ATP consumption and promoting ATP generation.
As a regulator of energy homeostasis, AMPK has been suggested to be a potential drug target for metabolic syndromes including type II diabetes, cardio-vascular disease, and fatty liver disease. Many of the metabolic syndromes are linked to insulin resistance. Insulin resistance is a pathological condition in which cells fail to respond to insulin thus excess glucose in the blood stream cannot be removed into skeletal muscle or fat tissue. The activation of AMPK increases protein level of GLUT4, a glucose transporter, via transcriptional regulation and induces GLUT4 translocation to the plasma membrane in muscle cells in an insulin independent manner resulting in increases in the rate of cellular glucose uptake. Activation of AMPK also inhibits fatty acids and cholesterol synthesis via suppressing acetyl-CoA carboxylase and HMG-CoA reductase, respectively. In addition, activation of AMPK leads to inhibition of several transcription factors, including SREBP-1c, ChREBP and HNF-4a, and down-regulates the expression of enzymes which are mainly involved in fatty acid synthesis and gluconeogenesis. These findings support the idea that AMPK is a target of choice in the treatment of metabolic syndrome, in particular, diabetes.
AMP is the natural activator of AMPK in cells. However, it's an unstable compound and extracellular application of AMP might trigger purinergic receptor-mediated signaling (that might lead to apoptosis etc). As a result, many researchers have been devoted to AMPK activator development. Compounds such as 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) and metformin can activate AMPK at high concentration in vivo. Metformin has been used to treat pre-diabetes, insulin resistance, syndrome X and type 2 diabetes. However, its side effects include lactic acidosis, especially when patients have renal insufficiency. Developing novel AMPK activators with lower effective concentration and fewer side effects is therefore urgent.